1. Field of the Invention
The present invention relates to a blowing fan and, more particularly, to a blowing fan for a refrigerator capable of reducing a resonance noise according to a torsional resonance generated in driving a fan and avoiding a resonant frequency by lowering a torsional resonant frequency of a rotational shaft connecting the fan and a motor.
2. Description of the Background Art
In general, a refrigerator is divided into a freezing chamber for keeping frozen food items and a refrigerating chamber for keeping refrigerating food items, and includes a refrigerating cycle for supplying cooling air to the freezing chamber and the refrigerating chamber.
FIG. 1 is a front view of a refrigerator in accordance with a refrigerator.
The conventional refrigerator includes a main body 104 having a predetermined space for storing food items and a door 102 mounted at its front side for opening and closing; a freezing chamber 106 formed at an upper portion of the main body 104 and storing frozen food items; a refrigerating chamber 110 sectioned from the freezing chamber 106 by a barrier 108, formed at a lower portion of the main body 104, and storing refrigerating food items; and a refrigerating cycle for supplying cooling air to the freezing chamber 106 and the refrigerating chamber 110.
At a rear side of the freezing chamber 106, there is provided a space partitioned by a shroud 112, in which a heat exchanger 114 provides cooling air through heat-exchanging with a refrigerant, a axial-flow fan 118 blows air cooled while passing the heat exchanger 114 to the freezing chamber 106 and the refrigerating chamber 110, and a motor 120 is connected to the axial-flow fan 118 by a rotational shaft 122 to rotate the axial-flow fan 118.
As shown in FIG. 2, the axial-flow fan 118 includes a hub 150 into which the rotational shaft 122 of the motor 120 is fixed so as to receive a rotational force of the motor 120, and a plurality of blades 152 arranged at predetermined intervals at an outer circumference of the hub 150 and generating a flowing force.
The blade 152 is extended in a curved-surface form from the outer circumference of the hub 150, and in general, five blades are provided.
The operation of the refrigerator constructed as described will now be described.
When the axial-flow fan 118 is rotated according to driving of the motor 120, cooling air passes through the heat exchanger 114 and blows to the freezing chamber 106 and the refrigerating chamber 110, thereby performing a cooling operation. The cooling operation-completed air is sent back to the heat exchanger 114.
Since the refrigerator has a large capacity and its internal temperature is to be uniformly maintained to keep food items fresh for a long period, the method of discharging cooling air in several directions in the refrigerating chamber is adopted.
Accordingly, a cooling passage for guiding cooling air in each direction in the refrigerating chamber is long and complicate, generating much passage resistance to the flow of cooling air.
Thus, in order to smoothly and quickly circulate cooling air under such a high passage resistance, the axial-flow fan 118 needs to be rotated at a high speed. However, rotation of the axial-flow fan 118 at a high speed causes a torsional resonance phenomenon at the rotational shaft 122, which is a main reason of a noise of a refrigerator.
Thus, in order to solve such a noise problem, researches related to noise reduction are actively ongoing by using a shape designing of the rotational shaft 122 (notch, stepped shaft), a rotational inertia moment increase/decrease designing, or a coupling designing of the rotational shaft 122 and the axial-flow fan 118.
In this respect, however, in the conventional refrigerator, the design change in the rotational shaft 122 for the purpose of reducing the noise generated due to the torsional resonance phenomenon of the rotational shaft 122 necessarily accompanies a design change in parts coupled to the rotational shaft 122. Then, a unit cost would be increased, a productivity would be degraded, and a quality management wouldn't be easy due to the design change in many parts.